I need help! My roof won’t work on my 1996 XJS convertible. The 30 amp fuse is good and I have 12 volts there. The roof switch tests good. The car is in park and the handbrake is on with the light up on the dash. I have about four and a half volts on the connector to the roof switch, but it is negative voltage. Presumably it should be twelve positive. I have swapped the relays for the roof up and down—nothing. I have even swapped the controller for another— still nothing. What am I missing?
Bob

 

Have you checked that the Black/white wire has a negative/ground contact.

 

I’ll check that out. Thanks

 

Do you know anybody around Orlando who could look at this problem for me? I live in St Cloud.
Bob

 

Can you bring it to Sanford ?

 

Check the valve on top of the pump and make sure its not in manual.

 

Negative voltage (relative to chassis) does not exist on a car. So not sure what you are measuring.